Digital camera, imaging device and method for digital imaging

ABSTRACT

The invention relates to a digital camera, an imaging device and a method for dental digital imaging. One sensor is used for tomographic imaging and at least one sensor is used for transillumination imaging. The sensors are arranged to overlap each other. This arrangement provides a multiple use and a relative inexpensive camera compared with the ones using one sensor with a large area. Additionally, it is possible to arrange at least two separate electric connection structures for the different imaging modes. Further, its connection arrangements can be arranged in such a way that the mechanical connection structures of the camera are separated from the electrical connection structures.

This invention relates to a digital camera according to the preamble ofclaim 1, to an imaging device according to the preamble of claim 23, andto a method according to the preamble of claim 38 for digital imaging.

In particular, one of the objectives of the invention relates to dentalpanoramic and other tomographic imaging, and to a digital camera andimaging device used in cephalometric imaging, in which the area coveredby means for receiving the image information is essentially smaller thanthe projection of the object to be imaged on the image-forming surface.In this context, the image-forming surface denotes the virtual plane orsurface on which the projection of the object to be imaged is formed.

Further, the invention relates to a method for digital imaging in whichmethod the object to be imaged is radiated and the radiation is detectedby means for receiving the image information, the area covered by whichbeing essentially smaller than the projection of the object to be imagedon the image-forming surface.

Various tomographic and transillumination imaging methods are used inmany kinds of applications. Among others, in the medical andbiotechnological imaging applications, it is typical to direct x-ray,gamma, or beta radiation through the object to be imaged and further tothe image-forming surface. Digital imaging methods have been developedat the side of the traditional film-based imaging methods, and in thesemethods semiconductor sensors, such as CDD sensors (Charge-CoupledDevice) or CMOS sensors (Complementary Metal-Oxide Semiconductor) areused as image-forming surfaces. Typically, in such semiconductorsensors, x-rays are first converted to radiation the wave-length ofwhich is in the region of visible light but the developing technology isalso introducing sensors in which x-rays can be directly converted toelectric form.

Despite the many advantages offered by the digital imaging devices, theyhave not become as generalised as expected in so many visions. Theprices of digital cameras have been one of the essential factors havinghad influence on this. The semiconductor sensors used in the cameras aretypically made of silicon and, along with the growth of the size of thesensor, its manufacturing costs per surface area grow exponentially.This is why, in the applications requiring a wide imaging surface,cameras comprising of one semiconductor sensor will become veryexpensive.

The invention presented in this application has been developed in viewof the needs of dental x-ray imaging, and thus, it will be illustratedbelow primarily in the light of the applications of this field.Naturally, the invention is also suitable for use in connection withmany other imaging forms.

The dental x-ray imaging is divided in three main sections, out of whichin the so-called intraoral imaging it is typical to image individual, ora few teeth, in the so-called panoramic imaging the dental arch isimaged to a plane as a layer, i.e. as a tomographic image, and in theso-called skull or cephalometric imaging the skull area as a whole isimaged as a transillumination image. Further, many devices used forpanoramic imaging are suitable for taking even other cross sectionalimages of various areas of the dental arch. The present invention isparticularly suitable for use in connection with the panoramic and othertomographic imaging forms and with the skull imaging, all of which beingtypically made by the same imaging device. Particularly in thecephalometric imaging, the need for image information receiving meanswith large surface area has appeared problematic from the point-of-viewof the commercialisation of the digital imaging applications. Taking askull image with a sensor having a directly matching size with the areato be imaged would require use of tens of times bigger sensors astypically used in panoramic imaging.

As the dental skull image is a transillumination image it istraditionally taken by using so wide a beam and film that the desiredarea has been able to be imaged as one single shot. On the other hand,in panoramic imaging a tomographic image is typically produced by usinga narrow beam and the area to be imaged is scanned by it, whereby thetomographic effect for imaging the desired anatomic layer is created bycontinuously changing the entry angle of the beam in relation to theobject as the beam travels over the area to be imaged. In this so-callednarrow beam tomography method, the movement of the imaging means (theradiation source and the image information receiver) is implemented in acontrolled way so that the receiver is moving in relation to the beamwith a transversal speed corresponding the vertical scanning speed ofthe beam in the area to be imaged, multiplied with a magnifying factor,i.e. a coefficient that is the relation between the distance from theimage information receiver of the focus of the beam (=radiation source)and the distance from the area to be imaged. In this definition, thedetector primarily refers to the radiographic film, whereby, in thedigital imaging, the movement of the image information receiver inrelation to the anatomic layer to be imaged can be replaced by asuitable electric function, as a charge transfer on the surface of thesemiconductor sensor. Mathematically, this imaging equation can bepresented in the following form:V _(F)=(L _(FF) /L _(OF))×V _(O)where V_(F)=speed of film transfer, or an electric function by thesensor corresponding to it, L_(FF)=distance of film or any respectiveelement from the focus of the radiation source, L_(OF)=distance of theobject to be imaged from the focus of the radiation source andV_(O)=forward speed, parallel to the image-forming surface, of the beamin the object. Therefore, the precondition to a successful panoramicimaging is that, during the imaging, the respective positions of themeans to receive the image information, of the area to be imaged, andthe radiation source in relation to each other, continuously remain, asprecisely as possible, in compliance with this theoretical imagingequation.

In the digital panoramic imaging, the scanning movement of the beam isfollowed by a narrow sensor from which the image data is read out duringthe scan. As the panoramic and cephalometric images have typically beentaken by the same x-ray imaging device, it has been a natural idea touse the so-called scanning slot imaging technology also for taking thetransillumination images of the skull area (e.g. “Direct digitalextraoral radiology of the head and neck with a solid-state linearradiographic detector”, McDavid, W. D. et al., Oral Surg Med Oral Pathol1992; 74:811–7). This is how the sensor surface area needed for imaginghas been able to get considerably reduced. In some of such applications,however, the scan has been implemented in a way causing at leasttheoretical errors in the image, i.e. as the beam is positioned to meetthe image information receiver perpendicularly and the scanning of theobject is carried out by either conveying the object perpendicularlythrough the beam, or by positioning the object in a fixed position andby moving the radiation source and the image information receiver with aparallel synchronized movement past the object. These kinds of imagingmodes do not produce genuine transillumination images but, as a matterof fact, tomographic images where the size of the tomographic effectdepends on the width of the beam used. In addition to this, interpretingof the images obtained in this way is not familiar to the doctors, astheir projection geometry is different in the horizontal and verticaldirections, thus deviating from the traditional geometry of atransillumination x-ray image.

From the point-of-view of practical applications, use of the same sensorboth in the cephalometric and panoramic imagings would be desirable,among others regarding the administration of the camera production andthe sensor storage solutions, as the costs of starting the productionand, as the manufactured numbers would get larger, the costs per unit,could thus be reduced. In digital panoramic imaging the height of atypically used sensor is, regarding the cephalometric imaging, however,sufficient only in a few special applications, which is why twodifferent sensors have to be manufactured for the market. Therefore, thescanning slot imaging as such does not provide a solution based on whichone could manage with only one single sensor.

A feasible possibility as such would be to use a cephalometric imagingsensor in panoramic imaging in such a way that the sensor height wouldbe utilized only partly, but even this solution is problematic from thecommercial point-of-view. The sensor that is sufficiently high forcephalometric imaging is more expensive than two panoramic sensors,i.e., with today's prices, the camera needed for cephalometric imagingmight cost even more than the rest of the imaging equipment altogether.As typically only about one third of the panoramic devices are providedwith means for cephalometric imaging, regarding this and the pointspresented above, it is very understandable that the digitalcephalometric imaging applications have not become significantly moregeneral.

Use of the same digital camera for panoramic and cephalometric imagingshas been considered e.g. in the U.S. Pat. No. 5,579,366. Thispublication primarily discusses one dimensional digital cameras, to theevident idea of using a sensor that is high enough even forcephalometric imaging applications, i.e. a camera that is expensive andoverdimensioned from the point-of-view of the needs of mere panoramicimaging. In the scanning cephalometric imaging, a longer sensor than inthe panoramic imaging is needed, in any case, whether the imaging scanis made horizontally or vertically.

The actual invention according to the said U.S. Patent Publicationconcerns the camera interface arrangements that seem to be easy to useas such but that also include potential sources for problems. Use of thesame camera in different imaging positions requires its repeatedtransfer between the panoramic and the cephalometric imaging stationsand these measures will always imply a risk of damaging the expensivecamera, e.g. as a consequence of dropping it. Often repeated removalsand attachments set requirements of their own also to the mechanical,and particularly to the electric interface solutions of the camera. Inpractice, the problem of the interface solution according to the thepublication might prove to be the precise and steady positioning of thecamera in the imaging device, which is critical, in particular, inscanning slot imaging.

Also in connection with other imaging applications, different solutionshave been developed to solve the surface area/price problem of thesemiconductor sensors. Typically in these solutions, sensors coveringonly a part of the image-forming surface are used, which are then movedor transferred during the exposure, or between, individual exposures.E.g. in the mammographic devices different mosaic or chessboard patternbuilt sensors have been used, which are then moved between two orseveral different exposures. Typically, the different modularrealisations are expensive and to make them function in practice, too,the combination of the modules has to be carried out with extremeprecision—especially when the intention by combining them is toconstruct a uniform sensor surface based on modules.

The Patent Publication WO 95/12133 presents a modular sensorarrangement, based on the formation of a kind of zig-zag pattern, to beused in different radiographic and tomographic imaging applications.This as such technically excellent solution has not, however, been shownto become a commercial success, at least not in connection with medicalimaging—probably at least partly due to the fact that, e.g. a uniformpanoramic image cannot be achieved by this kind of a sensor. In thesensor arrangement according to the Publication, the sensor modules areall the time moving, in the direction of the scanning movement, indifferent stages, i.e. in relation to the rotational centre they are ineach moment of time in different positions and are continuously imagingthe object from different projections, i.e. they form images based ondifferent imaging geometries. Therefore, such a sensor arrangementcreates an image formed of stripes of the different projections,parallel with the scanning movement, where on the borders of them theremay be points of incontinuency. In particular, in the (dental) medicalradiographic imaging, these kinds of faults in images are notacceptable.

Therefore, the objective of this invention is to develop digital imagingtechnology to reduce the problems presented above. In particular, theobjective is to develop a camera that is relatively inexpensive tomanufacture and to acquire, suitable for scanning slot imaging, animaging device for the use of this kind of camera, and an imaging methodbased on a corresponding technology. In this way, the investments todigital technology, become more justifiable and the threshold for itsintroduction lower. The digital technology, among other, will make thedoctor's work easier as it enables getting images of better quality, andthus more precise diagnoses, but even saving the pictures andadministration of them in electric form—together with the rest of thedocumentation concerning the patients and the adminstration of thereception.

One of the objectives of the invention is to provide such a camera thatit can be used in more than one form of imaging, particularly in bothtomographic and transillumination imagings, especially in the sameimaging device, and possibly in its different imaging positions.Further, the objective of the invention also is to provide such a methodfor digital imaging according to which the same camera can be used totake both tomographic images and transillumination images—even ofobjects of different sizes.

Further, one of the objectives of the invention is to provide a camerathe sensor surface of which could simply and with moderate cost bemodified, implying that one of the objectives of the invention is toprovide this kind of a camera using a modular sensor arrangement. One ofthe additional objectives of the invention is to provide a modularsensor arrangement for the camera in such a way that the characteristicsof the camera can be easily changed, without the need to change itsbasic structure, when one further additional objective of the inventionis to provide the modular sensor arrangement for the camera so that itwill be easy to add modules to the camera in order to increase thesensor surface of the camera, or so that the way it is used can bealtered so that different imaging modes and imaging of objects ofdifferent sizes will be possible with the same camera.

A particular objective of the invention is to provide such a camerasuitable for dental panoramic and other tomographic imaging, that can beused, or that can be relatively easily and economically be modified sothat it will also be suitable for dental cephalometric imaging.

Further, one of the objectives of the invention is to provide a modularsensor arrangement for the camera so that the camera can be usedutilizing only a part of it, especially in tomographic imaging utilizingonly one module, that of the sensor arrangement.

One of the additional objectives of the invention also is to implementthe sensor arrangement so that the possibly broken individual sensormodule could easily be replaceable by a new one, possibly by a modulethat is identical with the other modules.

A further additional objective of the invention is to provide such amodular sensor system for the camera that the sensor surfaces of themodules and/or the circuit boards belonging to the modules can bepositioned also on different levels.

One of the special objectives of the invention is to provide an imagingdevice in which the same camera according to invention can be used forboth tomographic and transillumination imaging, in particular, for bothdental panoramic and cephalometric imaging.

Further, one of the additional objectives of the invention is to providesuch an imaging device whereby a camera according to the invention caneasily and safely be moved from one imaging station to another andpositioned precisely in its correct imaging position.

Further, one of the additional objectives of the invention is toimplement the camera connection arrangement so that it will consist ofat least two structurally different connectors, to connect the cameracorrectly to its imaging stations for at least two different imagingpurposes.

Further, one of the additional objectives of the invention is to providesuch an imaging device in the imaging positions of which, designed forat least two different imaging purposes, there are structurallydifferent connecting arrangements for connecting the camera to theimaging device.

Further, one of the additional objectives of the invention is to utilizethe connection arrangements of the camera to direct the imageinformation received from certain modules of the camera out from thecamera via signal paths exclusively assigned to these modules—inparticular, to direct the image information from one module fortomographic imaging out from the camera via a connection arrangementexclusively suitable for a tomographic imaging station.

One of the additional objectives of the invention is to realize theusability of the camera in more than one point of use so that theremoval and connection of it would include as few risks as possible fordamaging the camera itself, as well as its connecting structures.

Further, one of the additional objectives of the invention is to realizethe connecting arrangement of the camera so that its electric connectingparts would be as little vulnerable as possible to mechanical stressthat might, in time, damage them and lead to intermittent power contactfailures, or even to a permanent failure.

Further, one of the additional objectives of the invention is to realizethe connection arrangement of the camera so that it can be positioned toits imaging station relatively simply but in the same time as preciselyand for being as non-movable as possible.

Further, one of the additional objectives of the invention is to realizethe connection arrangement of the camera so that it will ensure a stableand safe mounting of it in the imaging device, in order to minimize theelectrical safety risks that could be caused by e.g. unusually strongexternal forces upon the camera. These forces can be caused by e.g.stumbling on the camera so that the connection structures would bend andcause shortcuts and thus potential damages to the imaging device and thecamera, or even personal injuries as a consequence of an electric shock.

Further, one of the additional objectives of the invention is to providesuch an imaging device where the connection arrangements intended forthe camera have been realized by using separate mechanical and electricconnection structures.

Further, one of the additional objectives of the invention is to realizethe connection arrangement so that its mechanical and electricconnection structures have been separated from each other, e.g. placedphysically on different surfaces of the camera housing.

Further, one of the additional objectives of the invention is to realizethe connection arrangement so that fixing of the camera will take placein a compulsory sequence of—positioning—locking of the mechanicalconnection—electric coupling.

The essential characteristics of the invention have been presented indetail in the attached claims. One of the main characteristics of theseis a modular sensor arrangement of a digital camera that consists of, inview of sensor surfaces or their projections on a certain plane, inparticular, the point projections in relation to the focus of theradiation source, an overlapping assembly formed by at least two sensormodules—or of a structure including at least the first module, and withmeans arranged for connecting at least another module functionally tothe structure to provide this kind of an assembly; whereby the firstmodule has been arranged to be used for scanning tomographic imaging,and whereby this said module has been arranged to be available forscanning transillumination imaging together with at least another sensormodule. In the same way, in the method according to thesecharacteristics, particularly one module unit of the modular sensorassembly is used for tomographic imaging, whereby this same module,together with at least another module belonging to this sensor assembly,is also used for transillumination imaging, whereby imaging of evenlarger areas than the areas that can be imaged by this first module willbecome possible.

In particular, the overlapping module assembly according to thisinvention means a sensor arrangement whereby the sensor modules havebeen positioned, in relation to each other, in an overlapping positionso that

considering the sensor surfaces of the sensor modules, or theirprojections on the plane formed by the axles y, z of a right-angled setof coordinates x, y, z,

whereby a projection here indicates, in particular, the point projectionwhich is imaged to said plane via the focus of the radiation source usedin the imaging and the said sensor surface,

each of them covers a different area on this plane, and that,

when proceeding in the direction of the axle y,

the projection, or the said point projection of the sensor surface, ofeach subsequent sensor surface placed on the plane formed by the axlesx, z, will cover a different area from the previous projection,

and that the projection, or the said point projection of the sensorsurface, of each subsequent sensor surface placed on the plane formed bythe axles x, y, will meet that of the previous projection—possibly by atleast partially covering the same area.

The modular structure according to this definition can therefore beimplemented so that, when proceeding in the direction of the axle y,each subsequent projection, on the plane formed by the axles x, z,covers a different area from the previous projection so that the bordersof these areas meet.

When the camera with the sensor arrangement according to the inventionis positioned in the imaging device using scanning slot technologyaccording to this invention, the direction of the scanning movement ofthe beam is the direction of the axle z of the definition above.

Thus, the sensor assembly can consist of only the first sensor moduleused for tomographic imaging and, in addition to this, the means, suchas the space required and the means attached to it for connecting atleast one another sensor module functionally to this arrangement, inorder to form an overlapping modular structure.

In the following, the invention will be described in more detail, usingits preferred embodiments and referring to the attached figures, out ofwhich

FIG. 1 shows a typical traditional panoramic and cephalometric imagingdevice,

FIG. 2 shows a structure of a camera housings according to theinvention,

FIGS. 3A–3E show some sensor module arrangements according to theinvention,

FIG. 4 shows a collimator system according to one preferred embodimentof the invention used to limit the beam of an imaging device,

FIGS. 5A and 5B show one way according to one preferred embodimentaccording to this invention to connect the camera to the panoramic andcephalometric imaging device, and

FIG. 6 shows a camera holder-connector structure in an imaging deviceaccording to one preferred embodiment according to this invention.

FIG. 1 shows one typical, traditional film-based panoramic andcephalometric imaging device comprising a body part 1, another body part2 movably attached to it, with further a suspension arm 3 movablyattached to the second body part 2, at the essentially opposite ends ofwhich the radiation source 4 and the image information receiver 5 usedin panoramic imaging are located. In the device according to FIG. 1,this image information receiver 5 is a film cassette, but it could also,respectively, be a digital camera attached to the suspension arm 3. Inaddition, positioning means for the object to be imaged are alsotypically used in panoramic imaging; their position in FIG. 1 isreferred to by reference number 6. To control the functions of thedevice, it also typically comprises a user interface 7.

To the device according to FIG. 1 are attached means for takingcephalometric images, when it also comprises another suspension arm 8with positioning means 9 for the object to be imaged in cephalometricimaging attached to it, as well as means 10 for positioning andattaching the image information receiver, which in the device accordingto FIG. 1 is a film cassette.

In addition, considering the digital application of this kind of device,a panoramic 11 and respectively a cephalometric 12 imaging station ofthe camera 5 have been indicated by reference numbers 11 and 12 inFIG. 1. These imaging stations will be later referred to in connectionwith the embodiments of the invention according to FIGS. 5 and 6.

When using the imaging device shown in FIG. 1, the object to be imagedis positioned either in a desired tomographic imaging position, in thearea indicated by reference number 6, between the radiation source 4 andthe image information receiver 5, or in a desired cephalometric imagingposition, by the positioning means 9 used in the cephalometric imaging.In tomographic imaging, a layer of the desired anatomy is imaged bymoving the radiation source 4 and the image information receiver 5 in acontrolled way on the essentially opposite sides of the object to beimaged so that at the same time the area to be imaged is scanned by anarrow beam. On the other hand, for cephalometric imaging, the radiationsource 4 is positioned to direct the beam towards the positioning means9 used in cephalometric imaging, and further towards the imageinformation receiver not shown in FIG. 1. The traditional film-baseddevices have typically had to be constructed so that the structures thatremain between the radiation source 4 and the cephalometric imagingstation 12, as the holder structures of the panoramic film cassette 5,or the like, have had to be moved aside when the device has been changedfrom panoramic imaging mode to cephalometric imaging mode. Inparticular, in applications using the same digital camera 5 this problemcan simply be solved by producing such a panoramic imaging station 11 ofthe camera 5 that removal of the camera 5 is sufficient to leave a freepath for the beam towards the camera 5 moved to its cephalometricimaging station 12.

FIG. 2 shows a structure of a camera housings 51 of a digital camera 5according to the invention. In this embodiment of the invention,respective apertures 53, 53′ matching the form of one of the sensormodule arrangements according to the invention have been arranged to theactual housing part of the camera 5, which is covered by an upholsterysurface which is permeable to the radiation used for imaging. Inaddition, camera 5 comprises means 60 for positioning and mechanicalfixing of the camera 5, to be later shown in more detail in connectionwith FIG. 6, and means 70 for electric connection of the camera, whichmeans can be implemented so that there are separate connecting means inthe camera, on one hand for different imaging modes, and on the otherfor electrical and mechanical connections of the camera to the imagingdevice.

FIGS. 3A–3E show some of the sensor module arrangements according to theinvention. In this context, by sensor module is meant any structureforming an essentially uniform sensor surface. The sensor module 20 maye.g. have the structure shown in FIG. 3A, of the sensor structure 21formed by four CCD microchips, optical fibre 22, scintillating material23, housing 24 of the sensor structure 21, cover 25 and a printedcircuit board (PCB) 27, or the like, coupled to this structure byelectric interface surfaces 26, but it may also consist of, e.g., asingle monolithic CCD chip.

The sensor module arrangement according to the invention may beimplemented in innumerable different ways out of which some have beenshown in FIGS. 3B–3E. These figures show the structure of camera 5 seenfrom the direction of the focus of the radiation source, when theradiation containing image information is directed via the apertures 53,53′ of the camera housing 52, essentially corresponding to the form ofthe sensor module arrangement of camera 5, to the sensor modules 20,20′, 20″, 20′″ that have been placed on the opposite inner wall inrelation to the apertures 53, 53′0 of the camera housing. A right-angledset of coordinates x, y, z according to the definition used above hasbeen added to the FIGS. 3B–3E, where the direction of the axle z is thesame as the direction of the movement of the camera, i.e. the scanningdirection of the beam, when the camera is used for scanning slotimaging.

FIG. 3B shows the simplest embodiment, consisting of two modules 20,20′, of the sensor module arrangement according to the invention. With acamera 5 consisting of this kind of a structure one is able to take atomographic image using one module 20, and a larger transilluminationimage by using also the other sensor module 20′ positioned inoverlapping relation to the first module 20. The stripe-forming effectencountered in tomographic imaging, where at any moment of time duringthe imaging scan the sensors are at different stages, can be controlledwithout problems in transillumination imaging. When the focus of theradiation source and the object to be imaged are held stationary and thescanning movement of the beam is implemented by collimators limiting thebeam, the modules moving synchronized with the scanning movement form atrue transillumination image, each of them at a certain stage of thescanning movement, i.e. e.g. when using the sensor arrangement accordingto FIG. 3B, when the modules pass the object from left to right, theupper part of the transillumination image will be completed later thanthe lower one. Even a long distance between the modules 20, 20′ in thedirection of scanning movement is not problematic from the point-of-viewof the formation of the final integrated image but, naturally, e.g. dueto the possibly uneven radiation output of the radiation source 4, orregarding the physical dimensions of the camera, this distance should,however, be left as short as will be reasonable, regarding the othersolutions of the camera arrangement. And, as in all slot imagingapplications of this type, it would also be preferred, in view of theobject not to move, to be able to have as short imaging time aspossible, i.e. to keep the distance in between the modules scanningdirection as short as possible for this reason, too.

If the projections of modules 20, 20′, on the plane formed by axles x, yat least partly cover the same area this will not cause any problems inthe formation of a transillumination image, as the overlapping parts canbe integrated by the image processing methods evident to those professedin the art, to appear as if they had been taken by one sensor. Thepartial images can be combined e.g. so that the image informationcorresponding to the part of the object that has possibly been imagedmore than once, due to the overlapping of the sensor surfaces, is eitherremoved from the information produced by all the modules except one, or,in particular, so that all of the information received is used informing the image and the part having been imaged more than once isscaled to correspond the image information that would have been receivedfrom only one sensor module. On the other hand, overlapping is alsouseful regarding the fact that then there will certainly not be left anygaps between the partial images formed by the separate modules. In somespecial imaging modes it may even be appropriate to arrange two ore moremodules to image, even totally, the same area, i.e. to arrange themodules so that, according to the definition used above, the projectionsof the sensors cover the same areas on the plane formed by the axles x,y.

According to the invention, the camera 5 may also include three, four,or even more sensor modules to form e.g. an over-lapping line accordingto FIG. 3C, a structure formed by sensor modules of different sizesaccording to FIG. 3D, or a structure formed by two columns according toFIG. 3E. Then, FIGS. 3D and 3E illustrate the possibility that,according to the definition used above, when proceeding in the directionof the axle y, the border of the area covered by each successiveprojection on the plane formed by the axles x, z can be at a distance indifferent directions from the border of the area covered by the previousprojection, compared with the previous projection and the one before it,and that these projections may cover, partly or even totally, the samearea. This kind of covering the same area cannot, however, be presentwhen proceeding in the direction of the axle y for any two successiveprojections.

FIGS. 3B to 3E only show some simple basic structures that cap becombined and extended in many different ways within the basic idea ofthe invention. Further, according to the invention, the sensor modulearrangement can also be realized e.g. by arranging the modules 20, 20′,20″, 20′″, and, in particular, their surfaces 23 receiving the imageinformation, on different planes, i.e. at different distances from thefocus of the radiation source. This can be realized e.g. by usingconnecting surfaces 26 of different lengths. On the other hand, usingconnecting surfaces of different lengths, it is possible to create astructure where the sensor surfaces are at the same level but where theprinted circuit boards 27, or the like, are at different levels. Thesetypes of arrangements allow more latitude for the implemention of theelectronics arrangements of the camera. The marginal magnification errorcaused by the position of the sensor surfaces at different distancesfrom the objects to be imaged can, if desired, be corrected e.g. by theimage processing methods known as such.

In order to achieve as effective sensor surface as possible intransillumination imaging using the sensor module arrangement accordingto the invention, it would be preferred to leave the possibleoverlapping portion of the sensor surfaces, naturally even for costreasons, as short as possible. In principle, the sensor modulearrangement could be realized so that, according to the definition usedabove, the projections of the sensor surfaces on the plane formed by theaxles x, y, would not overlap at all, i.e. that the distance betweenthem would be zero. A so precise physical positioning of the modules is,however, technically more difficult to achieve than e.g. an arrangementwhere the modules are positioned at least a little overlapping and thepossible extra overlapping will be taken into account in the imagingprocess, e.g. by using a suitable collimation of the beam. Furthermore,an overlapping of the size of at least one row of sensor pixels ispreferred also because the combination of images is then more easilyfeasible, using means offered by many as such known electronic and/orimage processing software solutions. Especially if the effective heightof the sensor arrangement does not belong to the critical developmentcriteria, the use of overlapping and its optimal magnitude can beconsidered in the light of any particular characteristics of therespective application.

Regarding the needs of dental imaging, it is preferred to arrange themodule used for tomographic imaging as the lowest module of the sensormodule arrangement, as in all other cases especially the imaging of thelower jaw onto the panoramic image is difficult to arrange. In thesetype of applications, it is also preferred to implement the sensormodule arrangement according to the invention so that two identicalmodules, possibly in overlapping positions, are used, and the physicaland electronic arrangements of the camera are implemented so that themodules can be easily removed and/or connected to the camera. Expressedmore precisely, this means that it will be possible, in the first stage,to arrange in the camera housing only the module needed for tomographicimaging, and the physical space needed for the transillluminationimaging module plus the necessary means for its positioning andfunctional connection to the camera. In this way, a panoramic camera isprovided with a relatively inexpensive acquisition price, and to which,however, another module needed for cephalometric imaging can later beconnected in a simple way. In addition to this, thus a damaged modulecan easily be replaced by a new one and if the damaged module happenedto be one used only for cephalometric imaging, the camera can still beused for panoramic imaging purposes even during the time the acquisitionof a new module takes. The price of this type of a panoramic camera canbe made to match the price of a conventional panoramic camera, i.e. thecamera will be significantly cheaper—due to its smaller sensorsurface—than a panoramic camera consisting of one sensor module thatcould as such also be used for cephalometric imaging. In addition, evenprice of a camera according to this invention, extended suitable alsofor cephalometric imaging, consisting of two relatively small sensormodules will, however, remain clearly lower than that of a one modulecamera of comparable size. Even in a more general consideration, asensor arrangement according to the invention can thus be realized sothat, for whatever single module or several modules used only fortransillumination imaging, only the physical space and the necessarymeans for connecting the module functionally to the camera are arrangedto the camera housing, in which case the sensor arrangement can bysimple connection measures be arranged to form a larger overlappingmodular structure.

According to the invention, there are numerous ways to remove or discardthe signal produced by other modules than that used for tomographicimaging from the image information used for creating the tomographicimage. E.g. the electronics arrangements of the camera can beimplemented so that the signal path to the transillumination imagingmodules can be cut, or so that the image is formed, or the image data istransmitted from the camera to separate image processing means only fromthe signal received from the tomographic imaging sensor. The non-desiredinformation can be sorted out and removed by using electronicsarrangements, known as such, e.g. in the logic circuit of the camera, orlater by image processing methods, known as such. In addition or besidesto these arrangements, it is also possible to proceed so that thecollimation arrangement limiting the beam of the imaging device isimplemented so that, when the imaging device is used for tomographicimaging, the access of radiation to other sensor modules is blocked.

Further, taking into consideration certain preferred embodiments to bepresented later, one possible solution is to arrange two sets ofseparate electric connection means for the camera, in which case thesignal paths can be arranged so that one connecting element will be inconnection only to the tomographic imaging sensor module and the otherboth to the tomographic imaging sensor module and at least to onetransilluminaton imaging sensor module—or then at least to one of theconnection means arranged for this type of module. Thus, when the firstmentioned electric connector is used for attaching the camera to thetomographic imaging position, automatically, only the image informationproduced by the tomographic image sensor module is obtained via thisconnector, as desired.

The final formation of the image may be done in ways known as such, e.g.by connecting the imaging device to a computer, whereby the memory andthe processing means of the computer can be utilized. The processingmeans can also be realized by e.g. a dedicated ASIC circuit (ApplicationSpecific Integrated Circuit), connected to memory means, e.g. RAMmemory. Naturally, and as already partially described above, manymeasures of the image information processing can already be carried outin the camera, e.g. specifically in the ASIC circuit arranged to thecamera. The formation of the final image information as such iswell-known technology to those professed in the art, and a more detaileddescription of it is not necessary for the implementation of theinvention. In principle, the camera may be made by arranging all meansrequired for the image formation in the camera itself when it could beconnected directly to the display device.

In the implementation of the invention, it is possible to utilize theCCD sensor technology known as such, having shown to be very useful ine.g. panoramic imaging. On the other hand, one interesting alternativealso is the use of a newer technology based on CMOS sensors and directdetection of radiation, as with them certain advantages can be obtainedas compared to the traditional semiconductor sensors. The CMOS sensortechnology as such enables, due to its so-called parallel bus type datatransfer system, a faster transfer of image information, and withsensors based on direct detection an even better resolution is achievedthan with the traditional semiconductor sensors, when there are noscintillating and optical fibre structures reflecting light also tonon-desired directions. The sensitivity of the sensors based on directdetection is better, too. The CMOS technology is the most commonlyapplied semiconductor technology and, because of this, the availabilityof CMOS circuits is good and their manufacturing costs are being reducedby the technical development.

One of the sensor technologies based on direct detection of radiationhas been described in more detail e.g. in the Patent ApplicationPublications WO 95/33332 and WO 97/20342. It is not possible to performa charge transfer function (Time Delay Integration=TDI) with this typeof a sensor, nor is there any simple way to construct such a function toit. However, this type of a sensor can be used in these imaging modes byforming the image so that an image of the object is produced every timethe object to be imaged, or the sensor, has moved about one pixelforward, and by adding these images to each other so that they are, atthe same time, overlapping a corresponding distance in relation witheach other.

FIG. 4 shows one preferred embodiment of the invention for a collimatorarrangement for limiting the beam, which in the situation shown in thefigure has been arranged to be ready for use in cephalometric imaging.In cephalometric imaging the beam received from the radiation source 4is first limited by a primary collimator 31 (collimator opening 31A)placed in the vicinity of the radiation source 4, and before the objectto be imaged 33 by another collimator 32 placed to a sufficient distancefrom the focus, which will limit the beam to essentially match the formof the areas 53, 53′ the camera housing, which are permeable toradiation. The scanning movement of the beam is realized by the movementof the collimators and the camera is moved synchronized with thismovement. If the sizes of the active surfaces 23, 23′ of the sensormodules 21 and of the areas 53, 53′ permeable to radiation, especiallytheir overlapping, are arranged to be larger than the effective sensorsurface 23, 23′ required in the respective imaging, with a suitablelimitation of the beam it will be possible to prevent the unnecessarydirection of radiation through the object to be imaged 33 twice, to thearea of the sensor surface not to be utilized in image formation, andthe image information of the area left outside the beam can be removedbefore the partial images are combined.

Panoramic imaging can be realized in a manner known as such by thestructure according to FIG. 4 by positioning the aperture 31B, intendedfor panoramic imaging, of the primary collimator 31 in the essentialvicinity of the radiation source 4 to limit the beam to match theconventional beam used in panoramic imaging, i.e. to essentially matchthe aperture 53 of the camera housing.

The FIGS. 5A and 5B show one of the preferred ways to attach the camera5 according to the invention to the imaging device. In the solutionaccording the figures, the camera 5 can be considered as positioned e.g.to its cephalometric imaging station 12 in FIG. 5A and to its panoramicimaging station 11 in FIG. 5B. In FIGS. 5A and 5B arrow 41 indicates theentry direction of the x-rays to the camera 5, i.e. the camera 5 and theconnection arrangements 42A, 42B of the imaging device have beenarranged to be of different structure, so that the camera 5 can, on onehand, only be mounted from one direction to the cephalometric imagingstation 12, and from the other direction to the panoramic imagingstation 11 (compare with FIG. 1). When the said directions have beenarranged horizontally according to FIGS. 5A and 5B, moving the camera 5between the imaging stations 40A, 40B is easy and fast, and at the sametime, the danger of dropping the camera 5 unintentionally has beenminimized. When positioning oneself to the area between the panoramicimaging station 11 and the cephalometric imaging station 11, 12, thecamera is easily removable from one imaging station and attachable tothe other imaging station by using a simple horizontal movement. In thisway, that critical time for the risk of damaging the camera 5 when it isnot safely mounted and secured to the imaging device, is reduced.

Technically, the imaging device according to the invention is,naturally, also possible to realize so that the scanning movement of thebeam is made in some other direction than horizontally. Especially, thepanoramic and cephalometric imaging devices according to the inventioncan be made so that the scanning movement of the cephalometric imagingis arranged to be done in vertical direction, whereby the sensor modulearrangement can be implemented in a somewhat shorter form.

FIG. 6 shows a connection arrangement 60′, 70′ enabling one preferredembodiment of the invention shown in FIG. 5 to fix the camera 5according to FIG. 2 to the imaging device. The structure shown in FIG. 6may be considered to correspond the panoramic imaging station 11according to FIG. 5B, when e.g. the respective connecting arrangement(60, 70) forming a structural mirror image may be arranged to thecephalometric imaging station 12. The connection arrangement 42Baccording to FIG. 6 consists means 60′ for positioning and mechanicalmounting of the camera 5 and means associated with the electricalcoupling 70′ of the camera. The camera 5 is brought to the imagingstation 11 in the direction of the guiding rails 61, 62 that ensure thecorrect positioning, from the opposite side of their end plate 63. Whenthe guiding rails 61, 62 have penetrated fully into the matching guidinggrooves in the camera 5, the fixing of the camera 5 can be secured byturning the locking means 64 to its locking position over the camerahousing 51. Additionally, the connection arrangement according to FIG. 6can also be made so that the electric connecting means 71, 72 are movedto contact the matching elements in the camera not until the camera hasbeen mechanically locked, e.g. with a perpendicular movement in relationto the direction of the positioning movement of the camera, which isrealized by a pressing element appearing from below of the locking means64. Thus, the sensitive electric means can be protected from mechanicalstresses by this kind of compulsory operating sequence ofpositioning—securing the mechanical connection—electric coupling. Inparticular, this kind of an arrangement enables the realisation of theelectric coupling and its switching off without any gliding movements ofthe connecting means. The connecting arrangement 42B according to FIG. 6does not cause mechanical stresses to the means 70 involved with theelectric coupling of the camera 5 and the imaging device even when thecamera is connected to its operational station. The mechanical stresseson the electric connectors are problematic, especially if the durationof them is long, as the connection elements may bend with time, orotherwise be damaged to the extent that the electric contact starts tofail, or even becomes cut off permanently.

As already partly described above, in the solution according to FIG. 6specifically horizontal rails have been used to reduce the possibilitythat the expensive camera would slip to the floor unintentionally duringits removal and/or mounting. On the other hand, intention in using morethan one guide rail, as well as in separating the positioning and theactual locking means to elements of their own, is to ensure the correctpositioning of the camera, regarding which in slot imaging, inparticular in the direction of the width of the narrow beam, one mustespecially precise. The solution according to FIG. 6 of separating theactual mechanical connection from the electric coupling also reducese.g. the imminent danger of shortcuts by unintentional crashes to thecamera that could lead to a consequence of damaging the camera, or theimaging device as a whole, or even to fatal danger in the form of anelectric shock.

The connecting arrangements 42A, 42B of the separate imaging stations11, 12 can be realized as structurally different so that the camera 5can be attached to one imaging station 11 only by using a connectionarrangement 60, 70 only compatible with it, and to another imagingstation 12 by using another connection arrangement. Thus it can beensured that the camera 5 will always be connected correctly to eachimaging station 11, 12. At the same time, the operational life time ofthe electric connectors will be increased when the number of times ofcoupling per connector structure is reduced to half, and even if,despite of the above, one connection arrangement would be damaged, thecamera could still be used at least in one of the imaging stationsduring the time the acquisition of a new camera, or in practice, mostlikely new connecting means, will last.

As a summary, it can be said that, according to the embodiment of theinvention shown in FIGS. 2, 5, and 6, there are structurally differentconnection arrangements for the tomographic and for thetransillumination imaging stations, whereby, respectively, there are twostructurally different connection arrangements in the camera, and theseconnection arrangements consist of separate mechanical connectionstructures and electric connector elements arranged as independentlyfunctioning elements, one for connection for tomographic imaging on onehand and the other for transilluminaton imaging connection on the other.The electric coupling means arranged to the imaging devices areconnected to means for moving them in order to move them into contactwith the coupling means located in the camera, and when the mechanicalconnection means are arranged to consist of separate positioning andlocking means for the mechanical connection, the camera according tothis embodiment of the invention can be attached to the imaging deviceby one connection arrangement consisting of two separate connectionstructures only to a certain kind of connection arrangement of theimaging station, and only using a compulsory operating sequence ofpositioning—securing the mechanical connection—electric coupling.

Although the invention has been described above mainly by usingpanoramic and cephalometric imaging applications as examples, it cannaturally also be used in connection with any other correspondingimaging applications. For example, according to the invention, anyradiation that can be detected by semiconductor sensors can be used.

The invention is especially useful in the imaging applications ofmedical technology where x-ray or gamma ray radiation is typically used,or in biotechnological applications where beta radiation is typicallyused. Further, the invention can be applied to industrial testing andquality control methods utilizing transillumination.

For those professed in the art, it is evident that, especially withdeveloping technology, the basic idea of the invention is realizable inmany ways, and the embodiments will not be limited by the aboveexamples, but they can vary within the scope of protection defined inthe attached claims.

1. A digital camera for dental imaging comprising: an image formingsurface; a first sensor module arranged on said image forming surface,said first sensor module being structured and arranged for receivingtomographic imaging information; a second sensor module arranged on saidimage forming surface, said second sensor module being structured andarranged for receiving transillumination imaging information; whereinsaid first sensor module has a bottom edge and said second sensor modulehas a top edge, said bottom edge of said first sensor terminatingvertically below the top edge of said second sensor module.
 2. Thedigital camera according to claim 1, further comprising: means forforming an image information signal from said tomographic imaginginformation received by said first sensor module.
 3. The digital cameraaccording to claim 1, further comprising: means for forming an imageinformation signal from said transillumination imaging informationreceived by said second sensor module.
 4. The digital camera accordingto claim 1, further comprising means for receiving the imaginginformation received by said first sensor module and said second sensormodule and forming a transillumination image corresponding to an areacovered by both of said first and second sensor modules.
 5. The digitalcamera according to claim 1, wherein each of said first and secondmodules have a sensor surface and each of said sensor surfaces arearranged on a y-z plane of a right angled x, y, z coordinate system,said first and second sensor modules being arranged such that aprojection of the sensor surface of the first sensor module taken alongthe x-y plane intersects with a projection of the sensor surface of thesecond sensor module taken along the x-y plane.
 6. The digital cameraaccording to claim 5, further comprising a plurality of additionalsensor modules, each one of said additional sensor modules beingarranged such that a projection of the sensor surface taken along thex-y plane intersects with a projection taken along the x-y plane of thesensor surface of a previous one of said plurality of additional sensormodules.
 7. The digital camera according to claim 5, wherein aperipheral perimeter edge of an area defined by a projection of thesensor surface of the first sensor module taken in the x, z plane isspaced from a peripheral perimeter edge of an area defined by aprojection of the sensor surface of the second sensor module taken inthe x, z plane.
 8. The digital camera according to claim 1, furthercomprising: at least a third sensor module; wherein each of said first,second and third modules have a sensor surface and each of said sensorsurfaces are arranged on a y-z plane of a right angled x, y, zcoordinate system, said first, second and third sensor modules beingarranged such that a projection of each sensor surfaces taken along thex-z plane intersects with at least one other projection of the othersensor surfaces taken along the x-z plane.
 9. The digital cameraaccording to claim 8, wherein at least two of said first, second andthird modules are arranged in a first column in the x-y plane and theother one of said first, second and third modules is arranged in asecond column in the x-y plane.
 10. The digital camera according toclaim 1, wherein said first and second sensor modules are substantiallythe same size.
 11. The digital camera according to claim 1, wherein saidfirst module is arranged vertically above said second module.
 12. Thedigital camera according to claim 1, further comprising: means foroperably connecting said camera to a display device.
 13. The digitalcamera according to claim 12, wherein said means for operably connectingsaid camera to said display device includes a first signal path fortransmitting image data to and from said first sensor module and asecond branched signal path for transmitting image data to and from saidfirst sensor module and to and from said second sensor module.
 14. Thedigital camera according to claim 12, wherein said branched signal pathincludes means for combining partial images produced by said first andsecond sensor modules to produce a transillumination image.
 15. Thedigital camera according to claim 12, wherein said means for operablyconnecting said camera to said display device includes separate meansfor mechanically connecting said camera to said display device and meansfor electrically connecting said camera to said display device.
 16. Thedigital camera according to claim 15, wherein said means formechanically connecting said camera to said display device includesmeans for positioning said camera.
 17. The digital camera according toclaim 12, means for operably connecting said camera to a display deviceincludes structurally distinct first means for connecting said camera tosaid display device for tomographic imaging and second means forconnecting said camera to said display device for transilluminationimaging.
 18. The digital camera according to claim 17, wherein saidfirst means for connecting said camera to said display device and saidsecond means for connecting said camera to said display device arelocated on different physical surfaces of said camera.
 19. An imagingdevice for dental imaging comprising: a radiation source for producing aradiation beam; an imaging station; a collimator structure for limitingthe beam received from the radiation source; means for mounting acamera; means for positioning the object to be imaged; means forreceiving image data from the camera comprising a first sensor modulearranged on an image forming surface, said first sensor module beingstructured and arranged for receiving tomographic imaging informationand a second sensor module arranged on said image forming surface, saidsecond sensor module being structured and arranged for receivingtransillumination imaging information; wherein said first sensor modulehas a bottom edge and said second sensor module has a top edge, saidbottom edge of said first sensor terminating vertically below the topedge of said second sensor module whereby portions of the first andsecond sensor are partially overlapping.
 20. The imaging deviceaccording to claim 19, further comprising: means for forming an imageinformation signal from said tomographic imaging information received bysaid first sensor module.
 21. The imaging device according to claim 19,further comprising: means for receiving the imaging information receivedby said first sensor module and said second sensor module and forming atransillumination image corresponding to an area covered by both of saidfirst and second sensor modules.
 22. The imaging device according toclaim 19, wherein each of said first and second modules have a sensorsurface and each of said sensor surfaces are arranged on a y-z plane ofa right angled x, y, z coordinate system, said first and second sensormodules being arranged such that a projection of the sensor surface ofthe first sensor module taken along the x-y plane intersects with aprojection of the sensor surface of the second sensor module taken alongthe x-y plane.
 23. The imaging device according to claim 19, whereinsaid first module is arranged vertically above said second module. 24.The imaging device according to claim 19, wherein the collimatorstructure is structured and arranged to enable the limitation of thebeam exclusively to the first sensor module during a tomographicimaging.
 25. The imaging device according to claim 19, furthercomprising: means for taking a transillumination image by carrying outthe scanning movement of the beam by keeping the focus of the radiationsource steady and by moving the collimation arrangement limiting thebeam in a synchronized way with the movements of the camera.
 26. Theimaging device according to claim 19, wherein said imaging station is atomographic imaging station, said imaging device further comprising: atransillumination imaging station; and wherein said tomographic imagingstation is arranged nearer to said radiation source than saidtransillumination imaging station.
 27. The imaging device according toclaim 26, wherein said collimator structure comprises a primarycollimator structure located in the vicinity of the radiation source anda secondary collimator structure located at a distance from saidradiation source in the vicinity of said transillumination imagingstation.
 28. The imaging device according to claim 27, wherein saidprimary collimator structure is structured and arranged to enable thelimitation of said radiation beam to essentially match the form and sizeof said first sensor module, and said secondary collimator structure isstructured and arranged to enable the limitation of said radiation beamto essentially match the overlapping portions of said first and secondsensor modules.
 29. The imaging device according to claim 26, furthercomprising: means for operably connecting said camera to saidtomographic imaging station. means for operably connecting said camerato said transillumination imaging station.
 30. The imaging deviceaccording to claim 29, wherein one of said means for operably connectingsaid camera to said tomographic imaging station and said means foroperably connecting said camera to said transillumination imagingstation comprises separate electrical and mechanical connection means.31. The imaging device according to claim 30, wherein said separateelectrical and mechanical connection means are structured and arrangedsuch that said mechanical connection must be connected prior to aconnection of said electrical connection means.
 32. The imaging deviceaccording to claim 30, wherein said mechanical connection meanscomprises separate positioning means and means for locking theconnection means in a connected state.
 33. The imaging device accordingto claim 30, wherein said camera and said mechanical and electricalconnection means are structured and arranged such that during a mountingprocedure of said camera the camera must be mounted following acompulsory sequence in which said mechanical connection is connected,said means for locking the connection means is locked, and the saidelectrical connection means is connected.
 34. A method for dentaldigital imaging comprising the steps of: arranging a radiation source toemit a radiation beam at an area to be imaged; arranging a collimatorstructure to limit said radiation beam; arranging a sensor assembly suchthat the same sensor assembly is utilized for taking both tomographicimages and transillumination images, wherein said sensor assemblyincludes a first sensor module structured and arranged for receivingtomographic imaging information and a second sensor module structuredand arranged for receiving transillumination imaging information, andwherein said first sensor module has a bottom edge and said secondsensor module has a top edge, said bottom edge of said first sensorterminating vertically below the top edge of said second sensor modulewhereby portions of the first and second sensor are partiallyoverlapping.
 35. The method according to claim 34, further comprising:forming an image information signal exclusively from the informationreceived by said first sensor module.
 36. The method according to claim35, further comprising: removing said information obtained from saidsecond sensor module to thereby form said image information signalexclusively containing information received by said first sensor module.37. The method according to claim 34, further comprising: combiningimage information received from said first and second sensor modules toform a transillumination image signal.
 38. The method according to claim37, further comprising: reading image information from different stagesof a scanning movement receiving by said first and second sensor modulesand then combining said information received from said first and secondsensor modules to form said transillumination signal; and removing anyduplicate information obtained from both said first and second sensormodules from said transillumination signal to thereby from a completetransillumination image.
 39. The method according to claim 37, furthercomprising: limiting said beam by said collimator structure before saidarea to be imaged such that a projection of said beam on said area to beimaged is substantially equal in size to a projection of said first andsecond modules on said area to be imaged.
 40. The method according toclaim 34, further comprising: providing means for operably connectingsaid camera to said display device including a first signal path fortransmitting image data to and from said first sensor module and asecond branched signal path for transmitting image data to and from saidfirst sensor module and to and from said second sensor module.
 41. Themethod according to claim 34, wherein each of said first and secondmodules have a sensor surface and each of said sensor surfaces arearranged on a y-z plane of a right angled x, y, z coordinate system,said first and second sensor modules being arranged such that aprojection of the sensor surface of the first sensor module taken alongthe x-y plane intersects with a projection of the sensor surface of thesecond sensor module taken along the x-y plane.
 42. The method accordingto claim 34, wherein said first module is arranged vertically above saidsecond module.
 43. The method according to claim 34, further comprising:limiting said radiation beam to match said first module during atomographic imaging and limiting said radiation beam to match said firstand second modules.
 44. The method according to claim 34, furthercomprising: conducting a transillumination scan by maintaining saidradiation beam and an object to be scanned stationary; and moving saidcollimator structure and the sensor assembly in a synchronized manner.